Details
Currently, the preview+encode pipelines are not optimized, given there is no
support for User-Allocated Buffers on Capture (and hence no zero-copy). For
example the following pipeline exhibits jerkiness on the preview display even at
500 kbps:

Given the encode demo seems to be doing better, it'd be good to complete the
work on user-allocated buffers and verify that it optimizes this use-case.

Details
Currently, the preview+encode pipelines are not optimized, given there is no
support for User-Allocated Buffers on Capture (and hence no zero-copy). For
example the following pipeline exhibits jerkiness on the preview display even at
500 kbps: